Combustion gas generator

ABSTRACT

A combustible mixture of air and fuel is provided to a chamber formed in a housing; the combustion chamber is of a specific shape, so arranged that, in longitudinal section, it has approximately the shape of a single turn spiral, with the fuel and supply means connected to the spiral at the point of the maximum rate of change of curvature of the spiral wall, and the outlet from the spiral being located such that its axis is shifted with respect to the location of maximum rate of change of curvature of the spiral, by an angle of over 180* and less than 300*, and preferably between 200* and 235*, for example about 217*; upon admission of pre-heated air and fuel, self-ignition will occur providing combustion gases in shock wave or surges.

United States Patent [191 Andersson COMBUSTION GAS GENERATOR [76] Inventor: Louis Andersson, Gotgatan 73 IV,

Stockholm, Sweden [22] Filed: Apr. 12, 1971 [21] Appl. No.: 133,321

[30] Foreign Application Priority Data Apr. 16, 1970 Switzerland ..5652/70 [52] U.S. CI. ..60/39.77 [51] ..F02c 5/10 [58] Field of Search ..60/39.77, 39.76, 60/247, 249

[56] References Cited UNITED STATES PATENTS 3,303,643 2/1967 Beardsley ..60/39.76 2,805,545 9/1957 Wilman ..60/247 2,796,735 6/1957 Bodine ..60/249 3,516,253 6/1970 Allport et al. ..60/39.77 2,612,749 10/1952 Tenney et al ..60/249 3,240,010 3/1966 Morrison et al ..60/247 FOREIGN PATENTS OR APPLICATIONS 1,191,202 10/1959 France ..60/39.76

111 3,733,820 51 May 22, 1973 OTHER PUBLICATIONS M. W. Thring, Ed. Pulsating Combustion N.Y. Pergamon Press, 1961, p. 152-154.

Primary Examiner-Carlton R. Croyle Assistant Examiner-Warren Olsen Att0rneyFlynn & Frishauf [57] ABSTRACT A combustible mixture of air and fuel is provided to a chamber formed in a housing; the combustion chamber is of a specific shape, so arranged that, in longitudinal section, it has approximately the shape of a single turn spiral, with the fuel and supply means connected to the spiral at the point of the maximum rate of change of curvature of the spiral wall, and the outlet from the spiral being located such that its axis is shifted with respect to the location of maximum rate of change of curvature of the spiral, by an angle of over 180 and less than 300, and preferably between 200 and 235, for example about 217; upon admission of pre-heated air and fuel, self-ignition will occur providing combustion gases in shock wave or surges.

12 Claims, 2 Drawing Figures COMBUSTION GAS GENERATOR The present invention relates to a combustion gas generator, and more particularly to an apparatus to provide high-temperature gases, from which energy can be extracted, which are generated by self-ignition in a combustion chamber to provide shock waves, or surges of the hot gases.

Combustion gas, or hot gas generators are known; in previous constructions, a longitudinal combustion tube has been provided in which pulsating combustion sequences occur, ignition of the combustible mixture being obtained by periodic pressure variations occurring within the tube itself. Such hot gas generators have not found favorable acceptance because the thermal efficiency thereof is low, and because other technical difficulties in maintenance and construction inhibited wide use.

It is an object of the present invention to provide a hot gas, or combustion gas generator which has high thermal efficiency and which is simple in construction.

SUBJECT MATTER OF THE PRESENT INVENTION:

A housing defines a combustion chamber which, in longitudinal cross-section is approximately in the form of a single turn spiral. The supply for fuel and air is located at the point of highest rate of change of curvature of the spiral, and the axis of the outlet tube from the spiral is located with respect to the air and fuel inlets into the spiral-shaped chamber, that is, to the point at greatest rate of change of the spiral, offset by an angle of more than 180, but less than 300, for example within 200235.

Combustion chambers constructed in this manner are simple and provide a surprisingly high thermal efficiency. Auxiliary or separate ignition is not required, and no valves, flaps, or control or other pistons are needed. The structure itself. is compact and is essentially self-regulating, providing as much hot gas as is required by the unit to be driven, thus automatically supplying the required energy to a utilization device.

The invention will be described by way of example with reference to the accompanying drawings, wherein:

FIG. 1 is a longitudinal sectional view through the apparatus; and

FIG. 2 is a transverse sectional view along lines IIII of FIG. 1.

The apparatus is used to provide hot gases, for example to drive gas turbines, stationary or vehicular drive apparatus or flow machines, or it can be used to provide hot gases for reaction propulsion, for example for aviation use. It is essentially formed of a housing made ofa material which is highly heat-resistant, such as steel castings, light metal castings or the like. The housing is formed of two essentially symmetrical half-elements, to be interconnected in rigid, and gas-tight manner. The interior of the housing 1 is formed with a combustion chamber 2, having a longitudinal or plan outline in the form of a single-turn spiral, as seen in FIG. 1. The point of maximum rate of change of curvature of the spiral is indicated at 3; the inlet for air, or combustion gas 4, and the inlet of the fuel supply tube 5 are located at that point. The outlet 7 of the spiral has a major axis X which is offset by an angle a which is greater than 180, but less than 300, the angle being related to the center 6 of the combustion chamber 2 with respect to the region 3 of the chamber 2. Thus, the angular difference between the point of greatest rate of change of curvature 3 and the center of the outlet 7 is more than half but less than five-sixth around the circumference of the spiral; preferably, the angle a is between about 200 235, and in a preferred form is approximately 217.

The combustion chamber 2 is defined at the outside by a wall 8 which, in its transverse cross-section (see FIG. 2) is shaped to be approximately semi-circular. The adjacent side walls 9 of the combustion chamber 2 are slightly outwardly bulged to provide better resistance against internally arising pressures. A discshaped ring 10 extends into the interior of the combustion chamber 2, located in the separating plane of the two halves of the housing. The width inwardly extending portion of the ring 10 corresponds approximately to the radius of curvature in transverse section, of the semi-circular portion of the wall 8.

Spaced from wall 8 is a second outer wall 12 which is likewise approximately semi-circularly shaped, to de fine between walls 8 and 12 a chamber which is separated by a separating ring 13 into two chamber parts 14, 15. Both of the chamber parts 14, 15 surround the combustion chamber 2 from the outside and provide for pre-heating of the gas to be supplied to the combustion chamber. The gas itself is provided to the combustion chamber from a compressor, or supercharger 16 at some small pressure, with respect to ambient air pressure; this gas, typically air, is supplied to the combustion chamber 2 at the specific location of the maximum rate of change of curvature 3. The compressor or supercharger 16 can be of any known construction. The outer wall 12 of both halves of the housing is formed with connecting projections and eyelets 17 so that the halves can be screwed together by screws 18, to hold the halves together with a rigid, gas-tight connection. The separating ring 13, and ring 10 may form a single unitary structural element.

Flat end chambers 21 are formed between the end walls 20 and walls 9; the end chambers 21 are filled with steam or water vapor which, through fine nozzles 22, is injected into combustion chamber 2 in the form of spray or stream of steam, in order to improve the combustion process.

Compressor or supercharger 16, or other similar compressors, can be secured to the housing 1 by means of a somewhat tangentially projecting rod 24. Rod 24 is located in the interior, preferably coaxial, with a tubular fresh air duct 26 which communicates with the suction side of the compressor 16. Compressor 16, if constructed in accordance with the aforementioned application, reverses the flow of air being compressed and supplies compressed air, in counterflow, to the combustion apparatus as indicated by arrows C, and C The compressed fresh air is directed about the outside of the inlet duct 26 and supplied through duct 28 into chambers 14, 15. The compressor itself can be driven independently; in accordance with a preferred form of the invention, the compressor is driven by means of a portion of the hot gases derived directly from the combustion apparatus. To this end, a portion of the outlet 7 is separated, for example as schematically indicated at 7', FIGS. 1, 2, to direct hot gases to a turbine wheel connected to a rotating structure within compressor 16; about 10-15 percent of the hot gases generated in the gas generator of FIGS. 1 and 2 are suitably conducted to a turbine T to drive the compressor. Other compressors than that described in the application can be used, for example axial flow compressors or fans supplying air at an elevated pressure level to the combustion chamber.

Fuel, such as gasoline, benzine, kerosene, or the like, or other inexpensive liquid fuel is supplied byv a pair of parallel tubes 5. These tubes 5 are located partly, at least, within the interior of chambers l4, in order to preheat the fuel being supplied (omitted from FIG. 2 for clarity). A nozzle 30, forming a carburetor or spray or atomizer end is located at the terminal end of tube 5 which, as noted, is placed at. the point of maximum curvature 3 of the spiral. Nozzle preferably includes a small conical element inserted into tube 5, and pointed inwardly, and having a small opening at the tip thereof, to provide good spray and atomization of fuel derived from fuel line 5.

The amount of hot gases generated, or the gas pressure, respectively, within the combustion chamber 2 can be controlled by means of an eccentric element 31 located immediately adjacent point 3. The inner wall portion, close to point 3, is swingably mounted over a pivot 38, the position of the pivot being controlled by an eccentric element 31. Changing the position of the wall portion between the end of the wall and the remainder of the wall by swinging about swing point 38 changes the pressure distribution and thus the quantity of the hot gases generated within the chamber and removed through outlet 7.

The transition point from chamber 2 to the outlet tube 7 is rounded, as at 34, so that as little additional turbulence is introduced as possible, and so that the flow through the outlet tube will be as little turbulent as can be obtained. The diametrically opposite tip of the outlet tube 7 is extended into a somewhat spoonshaped projection 35. Projection extends into the outlet tube 7 and further contributes to directing a major portion of the pressure waves arising within chamber 2 into the outlet tube 7.

At the point of maximum curvature 3, a slight dead space will be formed. This dead space 40 arises due to the U-bend in the shaped wall 8. The dead space 40 is closed off by a plate member 36.

The cross-sectional area of the outlet tube 7 is preferably selected to be comparable to the cross-sectional area of chambers 14 and 15 taken together. The shape of the combustion chamber 2 can be selected to be a spiral with uniformly changing rate of curvature; due to manufacturing techniques, it is much simpler to make the chamber, however, in such a manner that approximately three quarters of the circumference of the combustion chamber is a pure circle having a center 6, and such that only the portion within the included angle defined by lines Y and Z and indicated as angle ,8 differs from circular shape. The largest diameter D of the combustion chamber, that is, the diameter measured in a vertical plane transverse to axis X is approximately 2-2 times the greatest width W of the combustion chamber; preferably, the relationship is about 1 2.5.

OPERATION:

Hot energy-supplying gases are generated by supplying from compressor 16 fresh air into chambers 14, 15, with a slight amount of pressure above atmospheric. Theair, while being supplied through chambers 14, 15, is preheated. This pre-heated air, being supplied to the terminal end 4, terminating in the combustion chamher, carries fuel from nozzle 30, in finely atomized form, into the combustion chamber. The quantity of air and fuel is selected to be an explosive mixture. This explosive mixture is highly subject to self-ignition; upon ignition, an explosion-like shock wave will occur within the combustion chamber 2, which propagates itself at the radially outer wall of the chamber 2, that is, along the inner side of wall 8. This shock wave or surge propagates in the progressive, circular eddy and the shock wave travels in the direction towards the outlet 7. This direction, that is, the direction of arrow A, obtains due to the change in curvature, and particularly since it is derived at the change of maximum curvature 3. Propagation of gas pressure in the contrary directionis inhibited by the sudden change in rate of curvature at point 3, and by plate 36. The thus arising shock wave or surge continues within the outlet tube 7; the major portion is conducted to a utilization device, for example a gas turbine, a propulsion nozzle, a thrust jet or the like. Not all the gases thus obtained will reach the outlet tube 7. The excess continues along the circular path at the inside of the wall 8, in the direction towards the point 3.

Upon surging past point 3, new fresh air will be sucked out of chambers 14, 15, together with new fuel from nozzle 30, causing a renewed, self-induced ignition. It is believed that this ignition occursdue to compression, and increase of density of the gas by the preceding pressure shock wave. Thus, a sequence of explosions will occur in short intervals, without requiring outside auxiliary ignition, or valves for the supply of specific amounts of fuel and air. This phenomenon has been referred to as pulsing combustion, or shock wave, surge, or percussion combustion.

To start the apparatus, a pump (not shown) supplies a little amount of fuel to chambers 14, 15, which fuel is ignited so that heat will be generated within chambers 14, 15. Generation of heat causes a comparatively small amount of air to move in the direction of the jump at the rate of curvature 3 which will carry along fuel from fuel pipe 5. This fuel already has been preheated due to heat exchange with the heated air in chambers 14, 15. When sufficient fuel is ejected from nozzle 5 so that the air-fuel mixture is of the proper ratio, and as the pressure wave builds up within the chamber, an initial spontaneous ignition will result and an initial cycle, as above described, will occur. As soon as the first initial ignition has been effected, subsequent ignition cycles follow automatically, without the addition of auxiliary fuel into chambers 14, 15, to heat the air therein so long as sufficient fuel is supplied through supply pipe 5 to chamber 2.

The gas is generated essentially under automatic selfcontrol. If there is little utilization of the combustion gases, pressure will build up within the interior of combustion chamber 2, which counteracts carrying along of fresh gas from chambers 14, 15, and, as a result, fuel from pipe 5. If, on the other hand, combustion gas is required in greater quantities, that is, if a larger amount of combustion gas is withdrawn from outlet 7, the pressure within chamber 2 will drop and more fresh gas will be sucked up from chambers 14, 15, which, in turn, will cause more fuel to be injected from pipe 5 and nozzle 30, so that the quantity of combustion gas being generated will increas.

The present invention has been illustrated as a combustion or hot gas generator to develop hot gases for hot gas engines, or other uses. Various changes and modifications may be made within the inventive concept, and to adapt the invention to specific uses or to other supplies of air, gas and fuel.

I claim:

1. Combustion gas generator in which a combustible mixture is burned by self-ignition to provide shock waves, and surges of burnt, hot gases, comprising a housing (1) defining a combustion chamber (2) having a wall which, in longitudinal section, has ap proximately the shape of a single-turn spiral, said spiral having at selected points of its circumference, different rates of change of curvature;

air (4) and fuel (5) orifice means connected to the spiral at the point (3) of maximum rate of change of curvature of the spiral housing wall, said combustion chamber (2) having an outlet (7) for removal of burnt gases in shock wave, or surge form, said outlet (7) being connected to said combustion chamber at a point such that its major axis (X), relative to the center of the spiral, is shifted with respect to the location of maximum rate of change of curvature of the spiral by an angle (a) of over 180 and less than 300.

2. Gas generator according to claim 1, wherein the angle (a) between the maximum rate of change of curvature of the spiral (3) and the axis of the outlet for the burnt gases (X) related to the center of the spiral is between 200 and 235; and the axis (X) of the outlet for the burnt gases extends radially from the spiral, with respect to its center.

3. Gas generator according to claim 2, wherein said angle is about 217.

4. Gas generator according to claim 1, including preheat chambers (14, surrounding said combustion chamber to pre-heat air supplied to said supply means.

5. Gas generator according to claim 4, wherein said fuel supply means comprises a fuel supply line (5), said line being located at least in part in at least one of said preheat chambers to pre-heat fuel being supplied to said combustion chamber.

6. Gas generator according to claim 4,'wherein the cross-sectional area of the outlet (7) from the combustion chamber for the combustion gases is approximately the same as the total cross-sectional area of said pre-heat chambers (14, 15).

7. Gas generator according to claim 1, in combination with an air compressor (16) wherein the housing of the combustion gas generator and said air compressor are rigidly interconnected.

8. Gas generator according to claim 7, wherein said compressor is a rotatable compressor, adapted to be driven by heated combustion gases, said compressor being interconnected (7') with the outlet (7) to receive part of the combustion gases from said generator to drive said compressor;

and said compressor is of the type receiving and delivering air in counterflow direction.

9. Gas generator according to claim 1, wherein the housing (1) is formed in two parts secured together at the median plane;

and a ring-shaped projection (10) extends into said chamber at approximately the median plane thereof.

10. Gas generator according to claim 1, wherein at least half of the circumference of the chamber, in longitudinal section, is approximately of circular form.

11. Gas generator according to claim 1, wherein the chamber, in transverse section, has an outer region which is approximately circular.

12. Gas generator according to claim 1, wherein the largest diameter (D) of the combustion chamber (2), measured in a plane transverse to the major axis (X) of the outlet (7) is about 2-3 times the largest width (W) of the combustion chamber. 

1. Combustion gas generator in which a combustible mixture is burned by self-ignition to provide shock waves, and surges of burnt, hot gases, comprising a housing (1) defining a combustion chamber (2) having a wall which, in longitudinal section, has approximately the shape of a single-turn spiral, said spiral having at selected points of its circumference, different rates of change of curvature; air (4) and fuel (5) orifice means connected to the spiral at the point (3) of maximum rate of change of curvature of the spiral housing wall, said combustion chamber (2) having an outlet (7) for removal of burnt gases in shock wave, or surge form, said outlet (7) being connected to said combustion chamber at a point such that its major axis (X), relative to the center of the spiral, is shifted with respect to the location of maximum rate of change of curvature of the spiral by an angle ( Alpha ) of over 180* and less than 300*.
 2. Gas generator according to claim 1, wherein the angle ( Alpha ) between the maximum rate of change of curvature of the spiral (3) and the axis of the outlet for the burnt gases (X) related to the center of the spiral is between 200* and 235*; and the axis (X) of the outlet for the burnt gases extends radially from the spiral, with respect to its center.
 3. Gas generator according to claim 2, wherein said angle is about 217*.
 4. Gas generator according to claim 1, including pre-heat chambers (14, 15) surrounding said combustion chamber to pre-heat air supplied to said supply means.
 5. Gas generator according to claim 4, wherein said fuel supply means comprises a fuel supply line (5), said line being located at least in part in at least one of said preheat chambers to pre-heat fuel being supplied to said combustion chamber.
 6. Gas generator according to claim 4, wherein the cross-sectional area of the outlet (7) from the combustion chamber for the combustion gases is approximately the same as the total cross-sectional area of said pre-heat chambers (14, 15).
 7. Gas generator according to claim 1, in combination with an air compressor (16) wherein the housing of the combustion gas generator and said air compressor are rigidly interconnected.
 8. Gas generator according to claim 7, wherein said compressor is a rotatable compressor, adapted to be driven by heated combustion gases, said compressor being interconnected (7'') with the outlet (7) to receive part of the combustion gases from said generator to drive said compressor; and said compressor is of the type receiving and delivering air in counterflow direction.
 9. Gas generator according to claim 1, wherein the housing (1) is formed in two parts secured together at the median plane; and a ring-shaped projection (10) extends into said chamber at approximately the median plane thereof.
 10. Gas generator according to claim 1, wherein at least half of the circumference of the chamber, in longitudinal section, is approximately of circular form.
 11. Gas generator according to claim 1, wherein the chamber, in transverse section, has an outer region which is approximately circular.
 12. Gas generator according to claim 1, wherein the largest diameter (D) of the combustion chamber (2), measured in a plane transverse to the major axis (X) of the outlet (7) is about 2-3 times the largest width (W) of the combustion chamber. 